Telegraph circuits



Dec.1.1931. I F. w JABvls 1, 7

TELEGRAPH CIRCUITS Filed Oct. 20, 1930 l NV E NTO R. FREDERICK W.JARV|SPatented Dec. 1, 1931 umrsu ST TES Parent OFFICE;

FREDERICK wiLLIAM JARVIS, or CROYDQN, sUnnnY, NGLAND, Assieno'n T0 03mini .AND COMPANY, LIMITED, or GROYDON, SURREY, ENGLAND 1 V TZEIAQEGRAVPHornot'rrrs I Application filed camber 2o,-193o, Seria1,No.;48 ,9 97,and'in Great. Britain-March 2c, 1930;. f

This invention: relates to telegraph systems I in which anintermediate'repeating station is connected between two terminalstations.

Telegraph systems in which signals are transmitted over a line only inone direction at any one time, are known as simplex telegraph systems.Telegraph systems in which signalsimay be transmitted simultaneously inopposite directions over a single line without mutual interference areknown telegraph systems. I

In simplex telegraph systems in which an intermediate repeating. station.:is connected between two terminal stations it is necessary ordesirable to arrange that either of the two receives. This necessitatesswitching operations at the intermediate repeating station at eachchange in the direction of transmission. In a double current systeminwhich signal-v ling is effected by currents of opposing polarity.which is the system in most general use, this is effected by automaticsend-receive switches, hereinafter referred to as autoswitches, at therepeating station which are controlled by relays, hereinafter referredto as auto relaysinserted in the line circuits in series withretransmitting relays, hereinafter referred to as transmitting relays.

In this case when one terminal station commences to transmit, thesignalling current operates the auto relay to one side and the other inresponse to signalling current from a neutral position. At each extremeposition a contact is made which closes the circuit of the auto switchwhich effects the appropriate switching operation for that direction oftransmission. The auto switches are slow to release, are therebymaintained operated during the transit periods of the tongue of the autorelay.

According to the presentinvention, in a double current telegraph systemin which switch means are required to be actuated to an operatedposition by signalling currents received over a line, means is providedto rectify the signalling currents in order to actuate the said switchmeans by unidirectional current.

The main advantage of this arrangement is as duplexthattheton'gue of theauto relay closes the I dur ng'slgnalhng, It lSJlSllfll tovmsert ashunted capacity at the receiving end of te1e graph .lines to improvethe speed of working by minimizing theflefiect of self induction ofthereceiving'app'aratus. In the present invention, the effect of thisshunted capaciity in series with the rectifier andthe transmitting relayis to increase the unidirectional holding current in the auto relayduring signalling reversals to an extent dependent on' the relativevalues of the capacity and re sistance and the electricalcharacteristics of the remainder of the line circuit, -.-The distinguishing feature of the invention is that thecontact on; the ,autorelayis now firmly maintained at high signalling speeds,-where-' aspreviouslythe duration of contact of the tongue with the limitingcontactstops was considerably reducedby the: transittime and contactbounce periodwhich increases with the speed of signalling. Further andconse quent. advantages will be apparent such. as

that due tothe reduced tendency to burning.

of the contacts and wearof the pivots of the relay;

The currentrectifier maybe of any convenient form but is preferably ofthe bridge type in which dry metal oxide rectifier elements are insertedin the armsof the bridge. The accompanying figure shows diagraminatically the connections at an intermediate repeating station in asimplex telegraph circuit according to the present invention.

A line 1 from a terminal station (not shown) isconnected to the armatureof an auto switch 2, the normal or back contact of which is. connectedthrough the winding of a. transmittingrelay 3, a shunted capacity 4,

and a bridge rectifier 5 to earth. The contacts of transmitting relay 3are connected to a split battery of, whichthe junctionis earthed, andthe tongue to the operated contactof auto switch 6, forthe other section7foftheline. A relay 8 is inserted in the bridge of the rectifier 5 andwhenop} erated closes the circuit through the winding of auto switch 6,which operates on the current from battery 9. The connections for theother section 7 of the line to the second terminal station (not shown)are similar to those for the first section. Line 7 is normally earthedthrough the winding of transmitting relay 10, shunted capacity 11 andrectifier 12. Relay 13 in the bridge circuit of rectifier 12 controlsauto switch 2 for section 1 of the line, and the tongue of transmittingrelay 10' is connected to the operated contact of the auto switch 2 ofthis section of the line.

Normally both the terminal stations would leave their terminal switches(not shown) to receive; This in efiect earths the two. sections of theline through the respective re-' ceiving means. Under thesecircumstances there is no current in either section 1 or7 of the lineand both auto switches 2 and 6 are ina'norinal or unoperated position sothateach section of the line is connected to earth at the repeatingstation through the respective transmitting relays 3 and 10, shuntedca-- pacit-ies 4c and 11, and rectifiers 5 and 12;

lV-hen a terminal station, for example the terminal station connected tosection 1, deslres totransmit, the switch at that terminal station isturned to send and a spacing current is, therefore, put on the line.

At the repeat ing station relay 8 thereupon operates and closes thecircuit of auto switch 6 which operates and connects the tongue oftransmitting relay 3' tothe second section 7 to. the line. Thetransmitting relay 3 responds to signal"- ling currents over section 1oi theline-and therelayed signals are retransmitted over the secondsection 7 to the second terminal eta-- tion. During signalling, aspreviously explained, the reversals of signalling currents are-rectifiedby rectifier 5 and maintains relay 8 in anoperated position, due to theefite'ct of the shunted capacity 4 in series in the line circuit, theholding current through the relay 8 is even increased during periods ofsignalling compared with the steady spacing current during pauses.

' It will be seen that this method of control.- ling of the auto switchby auto relays which are operated by rectified signalling currentsprovides switching means of a very robustnature compared with themethods previously known.

It will be understood that the actual connections at a simplex repeatingstation need not be precisely as shown in the accompany-- ing drawing.The general arrangements are well known. The invention which it is de--siredto protect resides in the manner of control of the auto switchesand is defined in the following claims.

'l/Vhat is claimed is:

1'. In a double current telegraph system, a, line circuit, switch meansactuated to an operated position by signalling currents received oversaid line, means to rectify said signalling currents to actuate saidswitch means by unidirectional current and hold said switching meansactuated during reception of signals, and a retransmitting relayresponsive to signals received over the line circuit to repeat signalsinto a line controlled by the actuated switching means.

2. In a double current telegraph system,

intermediate repeating apparatus connecting two sectionsoi a line,switclrmeans therein to. control the direction of retransmissioncurrent, rectifying means inserted in each section ofsaid line toconvert.signalling currents into unidirectional current, and meansresponsive to said unidirectionalv currentto control; said switch means.

In double current simplex telegraph repeating apparatus, a bridgerectifier, a shunted capacity and a winding of a signal retransmittingrelay together connected? in series: in each of two'secti'ons of a line,an auto relay connected in the bridge circuit of said rectifier andactuated to an operated position by signalling currents rectifiedthereby, and. an auto send receive switch controlled by each of saidauto relays.

4.. In double current: simplex telegraph repeating apparatus-a metaloxide bridge rectifier: connected in a line circuit, an auto relayconnected in the bridge circuit of said rectiher and; operable by linecurrents rectified thereby, and an. auto send-receive switch controlled.by said auto relay- In witness whereof I hereunto subscribe mynamethisfourthday of September, 1930.

FREDERICK \VILLLAM J ARVIS-

